PURPOSE: To improve the durability of the recording layer of the phase transition type optical disk to repetition of overwriting by decreasing the thermal damages incurred on the recording layer of the disk.

CONSTITUTION: Metallic layers 6 are provided right above or below the recording layer 3 of the phase transition type optical disk or both thereof. A protective layer 2 consisting of a ZnS.SiO2 thin film of 200nm thickness, the recording layer 3 consisting of an SbTeGe alloy thin film of 25nm thickness, the metallic layer 6 consisting of Si of 5nm thickness, an interference layer 4 consisting of a ZnS.SiO2 thin film of 25nm thickness, and a reflection layer 5 consisting of an Al alloy thin film of 150nm thickness are formed and laminated successively by a sputtering method on a transparent substrate 1 made of clean polycarbonate provided with guide grooves in, for example, Figs.. The heat generated in the recording layer 3 is partly diffused into the metallic layer 6, by which the thermal damages incurred on the recording layer are decreased.